Finding one's exact location in an unfamiliar city has presented a problem for both civilian and military populations. Discovering a location is even more challenging for the visually impaired. The visual clues used by sighted individuals in an unfamiliar place are useless to the blind pedestrian.
To provide the military with a location determination system, the U.S. Department of Defense has devised a system that can very accurately locate any point in three dimensional space. This system is known as the global positioning system (GPS).
There are twenty-four non-geosynchronous satellites circling the earth as part of a $12 billion Department of Defense location determination system. An accurate location can be determined by measuring the distance to at least three satellites. Since the signals produced by the satellites are not classified by the military, civilian companies have produced portable GPS receivers for determining exact locations on the earth. A GPS receiver can pinpoint a location on the earth to within about 100 meters. Using a technology called Differential GPS (DGPS), wherein fluctuations in the GPS location compared to a known true location are eliminated, an earth-bound location can be determined within about one meter. DGPS is a service provided by several vendors, wherein they broadcast GPS corrections on a sideband FM frequency. A user purchases a supplementary DGPS receiver that collects these corrections in real time.
Several commercial electronic maps using GPS technology have been produced. For instance, automobile guidance systems using technology from Etak Incorporated and Trimble Navigation have been distributed by a Toshiba/Blaupunkt venture. Etak produces digital map databases that are used to correlate GPS longitude and latitude coordinates with attributes on the earth. For example, the geographic coordinates of major roads and intersections are included in the database. Software developers use these databases to produce programs which correlate GPS coordinates with mapped locations in real time. Computer programs such as these have been used to track automobiles as they traverse city streets. These programs gather the fluctuating GPS coordinates as the car drives along a road, and correlate those coordinate locations on a stored map. A moving cursor indicates the automobile's position as it drives towards a destination. However, so far these systems have not been a major commercial success. It is possible that their commercial failure is related to substituting one hard-to-read map format (paper street maps) for another (street maps on a small computer monitor). It is also likely that such precision exceeds most practical uses.
In the commercial sector there are also several companies that have developed Microsoft Windows based electronic maps that accept GPS input. The Astia system from Liikkuva Systems International, (Cameron Park, Calif.) is an "executive" mobile computing system with integrated map that accepts GPS input. Astia includes a laptop computer that has a GPS satellite input and can continuously determine a user's position while driving along a street. A cursor shows the automobile's position on the map at any one time. An audio card can be purchased with the Astia system for verbally outputting the names of locations stored in the map database.
DeLorme Mapping (Freeport, Me.) has also built an automobile navigation system that relies on GPS technology. The DeLorme APS Mapkit SV is a software system that runs on a notebook computer. This system provides a user with an updated map of their position at any time. Their map includes over 1.1 million geographic and man-made features, including rivers, lakes, railroads, parks and monuments.
Technology has now progressed where hand-held GPS positioning products for hiking, boating or hunting are only $500-$1000. The Magellan GPS Trailblazer and Trimble Scout are hand-held GPS receivers that allow recording of paths between points and give bearing/distances to predetermined locations. However, these devices do not correlate latitude/longitude coordinates with locations on a pre-stored map. Without an integrated map database these products are limited to locating positions that have been input by the user. For instance, the location of campsites, cars and fishing holes can be input and then relocated on a subsequent trip. Although the hand-held systems are good tools for retracing a user's steps from/to a user-defined location, they rely heavily on the user's perception of location and mapping knowledge. The hand-held devices do not give the user an appropriate road to take to reach a desired location, only the straight line distance and direction. For this reason, they are not very helpful for getting a user to a specific point in an unknown city.
All of these systems have been designed with the assumption that the user is driving a car, or can see the features of the road or environment. In designing a system for the visually handicapped many other considerations must be addressed. Of course, paramount is a user interface that effectively communicates with the blind user. The majority of prior map location devices produce clear, full color maps of locations that are useless to a blind person. In addition, automobile direction systems are designed with the assumption that the car is always on a road. A blind pedestrian, of course, may be walking along a road, through an adjacent parking lot or in an alley.
In addition, map locations that are appropriate for a sighted driving person are likely inappropriate for a walking blind pedestrian. The locations that interest a blind pedestrian are normally within their close proximity. For instance, a blind pedestrian might want location updates every 250 feet, whereas a driver might only want to know their location every mile. In addition, landmarks such as mailboxes, bus stops and bridge overpasses are important to the blind pedestrian, but might be inconsequential to a person that is driving a car.
For this reason, the currently available geopositioning systems are unsuitable for the blind pedestrian. While others have proposed GPS type systems for the visually handicapped (Golledge et al. (1991) Int. J. Geographical Information Systems 5(4):373-394) an efficient system has not yet been developed. The present invention provides an accurate global positioning system for a blind pedestrian.